The present disclosure relates to a dot sighting device with a beam splitter.
In dot-sighting devices, there are cases in which an optical axis of a reflective mirror is inclined to an optical axis of a barrel of the dot-sighting device, and thus parallax is larger than in an optical system in which an optical axis of a reflective mirror matches an optical axis of a main tube. For this reason, in order to secure a region within allowable parallax, a distance between the dot reticle and the reflective mirror needs to be increased, or the effective diameter of the reflective mirror needs to be reduced.
FIG. 1 is a diagram schematically illustrating a dot-sighting device.
As illustrated in FIG. 1, a dot-sighting device 1 includes a dot reticle generating unit 5, a reflective mirror 7, and a fixing grill 11. The dot reticle generating unit 5 includes a light-emitting element such as a light-emitting diode (LED) and a mask having a transmitting portion of a dot reticle shape positioned in front of the light-emitting element. The reflective mirror 7 reflects light emitted from the dot reticle generating unit 5 toward the user, and transmits light provided from a target, and is fixed to the side of the front end at the target side. The fixing grill 11 is used to fix the dot-sighting device to a rifle or the like.
In the dot-sighting device 1, the user aims a rifle or the like at a target by causing a dot serving as a virtual image of a dot reticle reflected by the reflective mirror 7 to match the target.
Specifically, dot reticle beams emitted from the dot reticle generating unit 5 installed in the dot sighting device 1 are reflected by the reflective mirror 7 and enter on the observer's eye in parallel. An alignment is set to match a bullet firing axis of a gun barrel. If the angle of the parallelization of the reticle beams of the dot sighting device 1 does not match the bullet firing axis of the gun barrel, although the user causes a virtual image of the dot reticle emitted from the dot reticle generating unit 5 to match a target, a bullet does not hit the target. Thus, the optical axis of the barrel has to match the bullet firing axis of the gun barrel by operating a barrel aligning knob 3 having vertical and horizontal aligning functions.
In the dot-sighting device 1, as illustrated in FIG. 1, the dot reticle generating unit 5 is arranged at the edge of the barrel not to block the user's field of vision on the target viewed through the barrel.
The parallax of light rays in the periphery of the reflective mirror 7 decreases as an angle A1 between an optical axis C1 of the barrel 10 and an optical axis C2 of the reflective mirror 7 as illustrated in FIG. 2A.
A structure in which the optical axis C1 of the barrel 10 is aligned with or (matches) the optical axis C2 of the reflective mirror 7 as illustrated in FIG. 2B is smaller in parallax than a structure in which the optical axis C1 of the barrel 10 deviates from the optical axis C2 of the reflective mirror 7 at the angle A1 as illustrated in FIG. 2B. Thus, in the structure illustrated in FIG. 2B, it is possible to reduce a distance between the dot reticle generating unit 5 and the reflective mirror 7 to be smaller than in the structure illustrated in FIG. 2A, and a compact dot sighting device can be implemented.
However, in the structure illustrated in FIG. 2B, the dot reticle generating unit 5 is arranged on the optical path of the barrel 10 of the dot sighting device 1 and blocks the user's field of vision. Thus, the structure illustrated in FIG. 2B is rarely employed.
The reflective mirror 7 is coated to reflect a light ray having a wavelength band of the dot reticle generating unit 5. This coating reflects a light ray having the wavelength band of the dot reticle generating unit 5 among external light rays incident from the outside of the reflective mirror 7. The reflected external light ray is noticeable compared to other light rays, and thus the position of the user may be easily noticed by the opponents. For example, when the dot reticle generating unit 5 employs a red LED of 650 nm as a light source, a red light ray having a wavelength band of 650 nm among external light rays is reflected by the reflective mirror 7, and the entire reflective mirror 7 is viewed in red, and thus the position of the user is likely to be easily noticed by the opponents.